The present invention is directed generally to self-locking nut/sleeve assemblies for flared tube applications, and more particularly to a nut/sleeve arrangement which utilizes a tapered compression ring to achieve enhanced loading around the flare fitting.
FIG. 1 illustrates a conventional nut and sleeve assembly for flared tube applications (also referred to as a flared tube connecting assembly), generally designated as 500. The assembly consists of flared tube 502, nut 504, and sleeve 506. When pre-loading the nut 504 to a xe2x80x9cfinger tightxe2x80x9d (L1) state, the nut 504 is tightened to a predetermined torque value (L2). As a point of reference, sizes of xc2xdxe2x80x3 or less require less than 50xc2x0 rotation of the nut element when moving from condition L1 to condition L2. This results in approximately  less than 0.008 inches of thread advancement along the lateral centerline. Absent live loading, when subjected to vibration in addition to normal thread stretching and/or differential thermal expansion (DTE), the assembly is robbed of L1 and/or L2 values. Under these conditions, the tendency is for the nut 504 to loosen from the opposing male threaded element 508. The result of this condition is usually a loss of line pressure, leakage of liquids and possible shutdown of the system.
Current attempted fixes for the above noted conditions involve a variety of temporary solutions such as (1) the application of various xe2x80x9cdopexe2x80x9d compounds to the threads of the nut, with the attendant possibility of contamination the medium being transferred through the lines, (2) the application of lock wire devices, which must be monitored closely in order to eliminate the possibility of F.O.D. damage to the operating system, and (3) external clamping devices which are cumbersome and may require special application tools.
In view of the above, the present methods for securing an ordinary nut sleeve assembly as shown in FIG. 1 have not proven satisfactory in either form, fit, or function.
The present invention is directed to a self-locking nut/sleeve assembly which overcomes the disadvantages of the aforementioned devices in a practical and economical manner. The present invention includes a xe2x80x9clive loadingxe2x80x9d feature which is provided by a compression ring which is tapered at one end. The present invention requires a greater amount of rotation to go from an L1 to an L2 state than does a conventional nut/sleeve assembly. Additionally, the tapered compression ring results in a load that is more evenly delivered to the flared end of the tube. The present invention has the following additional advantages:
multiple connect/disconnect capability
no special tools required
no xe2x80x9clocking compoundsxe2x80x9d required
no lockwires required
available in sizes ranging from xc2xcxe2x80x3 to 3.0xe2x80x3in 0.062xe2x80x3 increments
built from readily available materials
constant live (compressive) loading of the nut assembly
In accordance with a preferred embodiment of the invention, a tapered compression ring has a generally ring-shaped body having (a) a gap or cut which defines a first end and an opposite second end, (b) a first face, (c) an opposite second face, and (d) a central axis. The first face is tapered toward the first end, and the body is twisted so that the first end is displaced from the second end along the central axis in a direction away from the first face.
In accordance with an important aspect of the invention, the first end is rounded.
In accordance with an important feature of the invention, the taper extends around about one quarter of the circumference of the tapered compression ring.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.